At Sun, 22 Sep 2019 23:02:04 -0300, Alvaro Herrera <alvherre@2ndquadrant.com> wrote in
<20190923020204.GA2781@alvherre.pgsql>
> On 2019-Sep-22, Dmitry Dolgov wrote:
>
> > > I think multiplying two ScanDirections to watch for a negative result is
> > > pretty ugly:
> >
> > Probably, but the only alternative I see to check if directions are opposite is
> > to check that directions come in pairs (back, forth), (forth, back). Is there
> > an easier way?
>
> Maybe use the ^ operator?
It's not a logical operator but a bitwise arithmetic operator,
which cannot be used if the operands is guaranteed to be 0 or 1
(in integer). In a-kind-of-standard, but hacky way, "(!a != !b)"
works as desired since ! is a logical operator.
Wouldn't we use (a && !b) || (!a && b)? Compiler will optimize it
some good way.
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center